Tech Induction Corporation (manufacturer) is proud to be trusted with the design, manufacture and repair of induction coils throughout the automotive and heavy-equipment industry. We have partnered our design and development capabilities with a tier-one Midwest automotive supplier to redevelop their spindle coils to add longevity and enhance performance. The following provides details of this collaboration and an outline for future developments.

With the budget belt tightening around everybody’s waist, suppliers and production facilities alike have been making strides to keep production rates down. Instead of passing rising operating costs onto our customers, the manufacturer looked into ways of providing them with a product of greater value. We started with the most frequently asked question – “How many parts or ‘shots’ are we going to get out of that coil?”

Fig. 1. Original part coil – life expectancy of 50,000 shots

Coil-Life Improvements

Coil life was a common problem for our customer, who specializes in the manufacture of automotive driveline spindles. These spindles are high-volume parts that run two or three shifts a day – on three dedicated, automated production lines – producing 7,500 parts each day. As you can imagine or are experiencing, the downtime caused by coil failure and multiple-part changeover when running this kind of volume is costly.

In today’s global market, competing for time is also competing for production dollars. Fifty-thousand shots per coil are no longer sufficient (Fig. 1). In years past, we considered this a good run for a hairpin or “stepped” single-loop machined-head coil.

Fig. 2. Cross section of coil and position relative to production part


With no change to the customer’s machine other than making sure we had enough cooling flow to meet our predetermined flow rate, we set off to redesign the coil(s) for increased production (Fig. 2).

Fig. 3. Coil developed using Ferrotron “559”

To sum up months of trials and testing in both our facility and our customer’s, we utilized the natural flow of current through the inductor. The benefit was twofold. One, it gave us enough heating surface to meet customer specifications without the use of laminations, which are costly and shorten coil life. Two, it prevented overheating of “thin” or protruding sections of the part, which was causing an undesirable microstructure. Using this simpler design and by diminishing the need for many brazed or machined pocket changes, a better coolant flow is maintained (Fig. 3).

Fig. 4. Cut part showing heat pattern

Additionally, this design allowed for application of Fluxtrol or Ferrotron where needed, either magnifying or shielding to create the desired heat patterns (Fig. 4). Replacing laminations with Ferrotron made for ease of production and application, and the continuous support of the Fluxtrol staff helps keep assembly costs to a minimum.

Fig. 5. New coil design with 400% improvement in life expectancy

Productivity Improvements

This is an automated facility, so seconds add up to minutes and minutes add up to money. We did not stop with the change in the coil design – now up to over 200,000 shots per inductor (Fig. 5). The goal was to look into moving parts through the machine faster. With induction hardening now down to 5.5 seconds, we recognized a problem of parts waiting to move through the cooldown shower before entering tempering. This caused a backup and uncontrolled temperature of parts entering the tempering inductor. This inductor was designed to do multiple parts, so there is no need for coil change in this station.

The inductor is used in unison with a four-sided quench box to achieve the desired hardness numbers, but it was still not enough to bring the spindle down to the desired temperature before tempering. By using a quench tube mounted to the inductor, we were able to cool the hollow part from the inside instantly after heating. This technique is used while hardening to controlled hardness depths, which proved beneficial for several part configurations. The part was able to cool down fast enough so there was no queuing of parts to enter tempering, which was part of the same automated system. Valuable seconds were eliminated from each hardening cycle, saving our customer money and allowing for more production per shift/day.

Part Setup Changeovers

With the benefit of quick-change receivers, hardwareless quench bodies, quick disconnect hosing and preset locating pins, part changeovers are no longer a three to four hour ordeal. It’s now down to a matter of minutes. Add this to a coil that lasts over 200,000 hits and an unforeseen problem arose. “How do we keep track of how old each coil is, and how many parts have been run with each coil?” Most machines have part counters registered on the output monitors. Once the coil is removed and the machine is reset, the information does not stay with the coil. Time is of the essence, especially in a production environment, and coils are changed out and placed on a shelf.

Fig. 6. Coil with counter inductor management

Maintenance Opportunities

When coils are being stored, it is a great time to perform coil maintenance procedures that the manufacturer helped to establish and document at the customer’s facility. As for the number of shots on each coil, we instituted the Independent Inductor Cycle Counter (IICC) program (Fig. 6). The IICC – attached to each individual inductor – cumulatively counts, displays and stores data for each energized heat cycle until inductor failure. A part date stamp is also recorded with each cycle. With this information, the manufacturer will trend inductor failure life span to continually work on improving coil life.

This is just one of the many scenarios we are faced with every day in trying to help our customers contain the cost of doing business in today’s ever-tightening global manufacturing environment. From the world’s largest heat-treat facilities to the smallest of job shops, Tech Induction is doing what it can to keep its customers in the race at a fair price.IH

For more information contact:Tech Induction Corp., 22819 Morelli Drive, Clinton Twp., MI 48036; tel: 586-469-8324; web:; e-mails: Darren Martens -; Eddie Sachs -; Chris Yakey - Additional contact information: Fluxtrol, Inc.: web:; e-mail: Rob Goldstein - and Powertrain Products & Chassis: web:; e-mail:

Additional related information may be found by searching for these (and other) key words/terms via BNP Media SEARCH at induction coil, driveline spindle, inductor, laminations